In the plastic injection molding industry, the rising costs of labor and materials coupled with competitive pressures and customer demands have created a need for a time and cost efficient method of producing mold assemblies for use in plastic injection molding. Most of the expense involved in working with mold assemblies occurs during the tooling process of the initial manufacture of the mold. Another expense results from the down-time which inevitably occurs during the repair, maintenance, or changing of the mold assembly.
In a majority of cases, mold assemblies are custom manufactured to certain specifications and then mounted to injection molding machines to produce a specific part or parts. The mold assemblies generally comprise two plates, oppositely positioned, with one plate allowed to move while the other is stationary. Plastic, or other material, is injected into the mold cavity between the plates, producing a plastic molded part. The molded part is then ejected from the mold assembly.
In order to reduce down-time, manufacturers have devised quick-change mold systems which provide mold assemblies that can be rapidly installed or removed from the injection molding machine. Examples of such systems are generally illustrated in U.S. Pat. No. 5,114,330, to Nielson; and U.S. Pat. No. 4,500,274, to Cyriax et al., both of which are incorporated herein by reference.
The Nielson patent generally describes an apparatus consisting of a plate receiving member mounted on a movable platen of the injection molding machine and a second plate receiving member mounted to one side and in alignment with the first member. A sliding frame plate, to carry one side of the injection molding machine and one set of mold modules, is then attached to the two plate receiving members to allow for a sliding action. The two mold halves are thus, in a relatively short amount of time, attached to the injection molding machine or removed therefrom minimizing the downtime of the machine.
The Cyriax patent employs clamping members rather than a sliding frame plate as used in the Nielson patent. These clamping members then connect or disconnect the plate receiving members with the injection molding machine which, again, allows for a relatively rapid replacement of the mold halves.
Although these systems provide a means for rapidly changing the mold assemblies on injection molding machines, these systems do not solve the problems associated with the expense of the initial manufacturing the mold assembly. Whenever a modification to the mold is desired, retooling of the entire mold assembly is still required. Another disadvantage of these systems is that they do not have the versatility to allow for different parts to be manufactured using the same mold assembly.
To address the problem associated with the time and expense of the initial manufacturing of mold assemblies, some mold manufacturers have chosen to use interchangeable base plates which accommodate different types of mold designs. Examples of such systems are generally illustrated in U.S. Pat. No. 4,795,125, to Boros et al. and the mold assemblies currently used by Master Unit Die Products, Inc. ("MUD"), incorporated herein by reference.
The Boros patent generally describes a method of manufacturing plastics or other materials comprising a mold assembled from repetitive modular standard elements consisting of substantially ready-to-use interchangeable base plates which carry the individually shaped (negative) mold or die cavity surface for forming the particular article to be manufactured. A similar method for manufacturing plastics and other similar type materials is currently employed by MUD. These interchangeable base plate systems allow for a larger number of applications by changing the various inserts within the system. This, in turn, reduces the potential costs involved in changing the mold assemblies for the particular applications.
One major disadvantage of the type of system described by Boros and employed by MUD is that the base plates must still be entirely exchanged. To accomplish this, the entire plate must be removed and re-installed with another in order to accommodate a different application. This process requires a substantial amount of time and effort.
Another disadvantage of this type of system is that it fails to address the problem of making various alterations and modifications, even minor ones, to the molded part once the mold assembly has already been manufactured. The current practice is to retool and manufacture a completely new plate to accommodate such a change, which is a time consuming and expensive process.
Advance Mold and Manufacturing, Inc. ("Advance Mold") has chosen to standardize certain frequently used injection molding frame elements and keep them in inventory in order to save the time and expense involved in manufacturing each part of the mold assembly on an individual basis. The standardized frame elements are then custom machined to the part specifications. By pre-fabricating frequently used frame elements and then stockpiling them in inventory, Advance Mold is able to reduce the downtime of the press inherent in the manufacturing process.
One major disadvantage to using the type of system employed by Advance Mold is that the initial time and expense of manufacturing a stock pile of standard frame parts is not reduced. Furthermore, it is still necessary to machine each frame element for the particular application. Another disadvantage to Advance Mold's system is that it does not allow for flexibility in adopting mold assemblies which are not in the current inventory. The frame elements to accomplish this must still be manufactured from scratch. Still another disadvantage to this type of system is that a substantial amount of time and effort is needed to change the frame elements in switching from one application to another.
One possible solution to these problems is to provide a single mold assembly which is universal and modular to reduce the initial manufacturing expense and to avoid the need for stockpiling multiple standardized assemblies.
Another possible solution to these problems is to provide a mold assembly which is universally modular in nature to accommodate the making of different molded products without the need for retooling or manufacturing of the entire mold assembly.
Another possible solution to these problems is to provide a mold assembly which could readily accommodate changes or modifications to a part design without the need for manufacturing an entirely new mold assembly.
Another possible solution to these problems is to provide a mold assembly with modular parts which can be quickly and efficiently changed to a new application thereby increasing productivity by reducing press downtime.
Thus, there has been a need in the art for single mold assembly which is universal and modular to reduce the initial manufacturing expense and to avoid the need for stockpiling standardized assemblies.
There is an additional need in the art for single mold assembly and which is universally modular in nature which accommodates the making of different molded products and allows changes or modifications to a part design without the need for retooling or manufacturing of the entire mold assembly.
There is an additional need in the art for a mold assembly with modular parts which can be quickly and efficiently changed to accommodate new applications.